Mass, volume and stress concentrators (geometry irregularities) affect the heat treatment process

Workpiece geometry variations will lead to differences in heat abstraction within the part during quenching, thus differences in volume of phase transformation, dimensions, residual stress affecting mechanical properties.

The main problem is that a part with a varying cross section is cooled throughout a quenching with different cooling rates. That results in undesirable formation of different microstructures and, therefore, different mechanical and physical properties. The other problem is residual stresses and a possible cracking.